Search around. Ask a few Realtors for their suggestions.
True story: My wife and I are doing extensive renovations on a rental property we own. It's a 3 bed/2 bath rambler built around 1950. We got bids of $45,000, $50,000, $60,000, and $130,000. (Yup, you read that right.)
We went with the $45,000 bid for a number of reasons, not just price. The house has two bathrooms: The original one from 1950s and one that was very poorly installed on the lower level probably around 1970.
We're having both completely redone. With the upstairs original bathroom, we ripped it down to the studs, but are putting everything back in the same places. With the downstairs bath, we totally ripped that out and are moving all sorts of things around. Both are very nice higher-end renovations.
The upstairs bath will cost around $8,000. The downstairs bath will cost around $10,000. If we'd wanted to economize, we could have save about $1,500 on each.
So: Ask a few Realtors for their recommendations. That's how we found our contractor.
Hope that helps.